Brillouin study of spin waves in sputtered CoNiPt alloy films

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Abstract
Sputtered CoNiPt films prepared for high-density magnetic recording media have been studied by Brillouin scattering. The spin-wave spectra in the film are remarkably broadened with width 13 GHz (full width at half maximum), which is much larger than the width of 3 GHz in a film prepared by vapor deposition. Observation by a transmission electron microscope has clarified that the sputtered film consists of Co crystallites with a diameter of 50–100 Å, which are separated from each other. The remarkable damping of the spin waves in the sputtered CoNiPt film is caused by the film structure. The film is, however, elastically homogeneous, which is known from the undamped surface acoustic wave spectra. The result shows the segregation of the nonmagnetic Pt-related alloys takes place between the Co crystallites. The exchange stiffness constant was determined as 2.4×10−9 Oe cm2 in the sputtered film, which is 1/1.7 that in the vapor-deposited films.